It has happened to me more than once. It doesn't matter if you have not given any signal to a girl, if she starts liking you she will try to establish ownership upon you in front of other females.

Cases being:

I was talking to a girl at the pub, I decided to go to the bathroom. There was a line for male bath because they were cleaning, she decided to go to the bathroom as well and got out while I was still in line. Without saying anything she decided to pass her arm around my waist as she passed by. When I got back it was obvious to me that she was flirting, I followed her game but when it was time to leave I just said goodbye and never asked for her number.

Other time I was walking in the streets with a female friend, it was very clear that we were friends. Suddenly this hot redhead appears in front of me and she smiled as we made eye contact, the girl I was walking with noticed and rapidly put herself in front of me (between the redhead and me) and I don't know what happened there but the redhead changed her expression and looked past us. Later this female friend tried to have sex with me by sending me articles saying "modern women can also request sex" and later by trying to get me drunk and sitting on my lap. I stopped drinking alcohol after this.

I have more, but I think I made my point. Women are very perceptive and jealous of other females, you may not notice but they have a lot of physical language that indicates how they are trying to claim ownership on you, language that other women can read easily. It's not rare for other women to assume a girl you're walking with is your girlfriend, that is because other women can read ownership hints.